resolve comments

Author: tianchen92

java/vector/src/main/java/org/apache/arrow/vector/ValueVector.java

@@ -238,9 +238,17 @@ public interface ValueVector extends Closeable, Iterable<ValueVector> {
    */
   boolean isNull(int index);
 
-  //TODO remove default and implement in subclasses
+  /**
+   * Returns hashCode of element in index.
+   */
   int hashCode(int index);
 
-  //TODO remove default and implement in subclasses
-  boolean equals(int index, ValueVector to, int toIndex);
+  /**
+   * Check whether the element in index equals to the element in targetIndex from the target vector.
+   * @param index index to compare in this vector
+   * @param target target vector
+   * @param targetIndex index to compare in target vector
+   * @return true if equals, otherwise false.
+   */
+  boolean equals(int index, ValueVector target, int targetIndex);
 }

java/vector/src/main/java/org/apache/arrow/vector/complex/FixedSizeListVector.java

@@ -45,6 +45,7 @@
 import org.apache.arrow.vector.types.pojo.DictionaryEncoding;
 import org.apache.arrow.vector.types.pojo.Field;
 import org.apache.arrow.vector.types.pojo.FieldType;
+import org.apache.arrow.vector.util.ByteFunctionHelpers;
 import org.apache.arrow.vector.util.CallBack;
 import org.apache.arrow.vector.util.JsonStringArrayList;
 import org.apache.arrow.vector.util.OversizedAllocationException;
@@ -503,7 +504,7 @@ public int hashCode(int index) {
     }
     int hash = 0;
     for (int i = 0; i < listSize; i++) {
-      hash = 31 * vector.hashCode(index * listSize + i);
+      hash = ByteFunctionHelpers.comebineHash(hash, vector.hashCode(index * listSize + i));
     }
     return hash;
   }

java/vector/src/main/java/org/apache/arrow/vector/dictionary/DictionaryEncoder.java

@@ -45,7 +45,7 @@ public static ValueVector encode(ValueVector vector, Dictionary dictionary) {
     validateType(vector.getMinorType());
     // load dictionary indices into a hashmap for lookup
 
-    DictionaryHashTable hashTable = new DictionaryHashTable(dictionary.getVector(), vector);
+    DictionaryHashTable hashTable = new DictionaryHashTable(dictionary.getVector());
     for (int i = 0; i < dictionary.getVector().getValueCount(); i++) {
       hashTable.put(i);
     }
@@ -71,7 +71,7 @@ public static ValueVector encode(ValueVector vector, Dictionary dictionary) {
       if (!vector.isNull(i)) { // if it's null leave it null
         // note: this may fail if value was not included in the dictionary
         //int encoded = lookUps.get(value);
-        int encoded = hashTable.getIndex(i);
+        int encoded = hashTable.getIndex(i, vector);
         if (encoded == -1) {
           throw new IllegalArgumentException("Dictionary encoding not defined for value:" + vector.getObject(i));
         }

java/vector/src/main/java/org/apache/arrow/vector/dictionary/DictionaryHashTable.java

@@ -74,12 +74,10 @@ public class DictionaryHashTable {
 
   private final ValueVector dictionary;
 
-  private final ValueVector toEncode;
-
   /**
    * Constructs an empty map with the specified initial capacity and load factor.
    */
-  public DictionaryHashTable(int initialCapacity, ValueVector dictionary, ValueVector toEncode) {
+  public DictionaryHashTable(int initialCapacity, ValueVector dictionary) {
     if (initialCapacity < 0) {
       throw new IllegalArgumentException("Illegal initial capacity: " +
           initialCapacity);
@@ -91,11 +89,10 @@ public DictionaryHashTable(int initialCapacity, ValueVector dictionary, ValueVec
     this.threshold = initialCapacity;
 
     this.dictionary = dictionary;
-    this.toEncode = toEncode;
   }
 
-  public DictionaryHashTable(ValueVector dictionary, ValueVector toEncode) {
-    this(DEFAULT_INITIAL_CAPACITY, dictionary, toEncode);
+  public DictionaryHashTable(ValueVector dictionary) {
+    this(DEFAULT_INITIAL_CAPACITY, dictionary);
   }
 
   /**
@@ -132,7 +129,7 @@ static final int roundUpToPowerOf2(int size) {
    * @param indexInArray index in vector.
    * @return dictionary vector index or -1 if no value equals.
    */
-  public int getIndex(int indexInArray) {
+  public int getIndex(int indexInArray, ValueVector toEncode) {
     int hash = toEncode.hashCode(indexInArray);
     int index = indexFor(hash, table.length);
     for (DictionaryHashTable.Entry e = table[index]; e != null ; e = e.next) {

java/vector/src/main/java/org/apache/arrow/vector/util/ByteFunctionHelpers.java

@@ -84,7 +84,10 @@ public static final int hash(final ArrowBuf buf, int start, int end) {
     return hash;
   }
 
-  private static int comebineHash(int currentHash, int newHash) {
+  /**
+   * Generate a new hashCode with the given current hashCode and new hashCode.
+   */
+  public static int comebineHash(int currentHash, int newHash) {
     return currentHash * 31 + newHash;
   }
 

java/vector/src/test/java/org/apache/arrow/vector/types/pojo/TestExtensionType.java

@@ -205,12 +205,14 @@ public UUID getObject(int index) {
       return new UUID(bb.getLong(), bb.getLong());
     }
 
-    @Override public int hashCode(int index) {
-      return 0;
+    @Override
+    public int hashCode(int index) {
+      return getUnderlyingVector().hashCode(index);
     }
 
-    @Override public boolean equals(int index, ValueVector to, int toIndex) {
-      return false;
+    @Override
+    public boolean equals(int index, ValueVector to, int toIndex) {
+      return getUnderlyingVector().equals(index, to, toIndex);
     }
 
     public void set(int index, UUID uuid) {